Radiation Protection Ch 7 Flashcards
The average energy deposited per unit length of track.
-units of kiloelectron per micron
linear energy transfer
electromagnetic radiation such as x-rays and gamma rays(short wavelength, high energy waves emitted by the nuclei of radioactive substances) this penetrating electromagnetic radiation is ionizing and interacts randomly along the length of its track
Low LET radiation
includes particles that posses substantial mass and charge. This type of radiation causes dense ionization along its length of track and is more likely to interact with biologic tissue
High LET radiation
Describes the relative capabilities of radiation with differeing LETs to produce a particular biologic reaction
Relatives Biologic Effectiveness (RBE)
when irradiated in oxygenated, or aerobic state, biologic tissues is more sensitive to radiation then when it is exposed to radiation under anoxic (without oxygen) or hypoxic (low oxygen) conditions
oxygen effect
the ratio of the radiation dose required to cause a particular biologic response of cells or organism in an oxygen-deprived environment to the radiation dose required to cause an identical response under normal oxygenated conditions
Oxygen Enhancement Ratio (OER)
biologic damage occurs as a result of ionization of atoms on master or key molecules (DNA) which can cause these molecules to become inactive or functionally altered
direct action
refers to the effects produced by reactive free radicals that are created by the interaction of radiation with water molecules
indirect action
solitary atoms or most often a combination of atoms that behave as extremely reactive single entities as a result of the presence of unpaired electrons
free radicals
single strand break- commonly occur with low LET radiation
point mutations
the loss or change of a base in the DNA chain
mutation
nondivision (nonmitotic) form of cell death that occurs when cells die without attempting division during interphase portion of the cell life cycle – programed cell death
apoptosis
exposing a cell to as little as 0.1 Gy(1 rad) of radiation just before it begins dividing can cause mitotic delay
- the failure of the cell to start dividing on time
mitotic delay
know the types of radiation that make up Low LET Radiation and high LET radiation
Low LET= x-ray and gamma rays (short wave length, high energy waves emitted by the nuclei of radioactive substances
High LET= includes particles that posses substantial mass and charge
know how free radicals influence biologic damage
dramatically increase
be able to describe how oxygen effects the biological tissues damaged by free radicals
Presence of oxygen in biologic tissues makes the damage produced by free radicals permanent.. Without oxygen damage produced by the indirect action of radiation on a biologic molecule may be repaired.
describe the indirect action of low LET radiation interacting with biologic tissue and causing damage
it causes damage to a cell primarily through an indirect action that involves the production of molecules called free radicals
the damage to molecules that happens when ionizing particles interact directly with vital biologic macromolecules such as DNA, RNA, proteins, and enzymes occurs from
Direct action: damage to these molecules occurs from absorption of energy through photoelectric effect and Compton interactions
what happens when free radicals act on a molecule such as DNA
the damaging action of ionizing radiation on the vital biologic macromolecule is indirect in that the radiation is not the immediate cause of injury to the macromolecule
what does the process of indirect action involve
the breakdown of a water molecule into smaller molecules, producing both ions and free radicals in the process
when does a cleaved or broken chromosome result
- when two interactions(hits) one on each of configuration
- each new portion containing unequal amounts o genetic material
know the 3 affects of ionizing radiation on chromosomes
- radiation induced chromosome breaks
- chromsomal fragments
- chromosome anomalies
be able to describe the Target Theory
A master or key maintains normal cell function is believed to be present and it is necessary for the survival of the cell. Because this molecule is unique in any given cell, no similar molecules in the cell are available to replace it.. If the master molecule is inactivated by exposures to radiation the cell will die
list how damage to a cells nucleus reveals itself
- instant death
- reproductive death
- apoptosis or programed cell death (interphase death)
- mitotic death
- mitotic or genetic death
- interference with function
- chromosome breakage
be able to describe instant death
occurs when a volume is irradiated with an x-ray or gamma ray dose of about 1000 Gy (100,000 rad) in a period of seconds or a few minutes
what happens to a cell when reproductive death occurs
the cell does not die but permanently loses its ability to procreate preventing the transmission of damage to future generations
when does mitotic or genetic death occur
when a cell dies after one or more divisions
what causes mitotic delay
exposing a cell to as little as .01 Gy (1 rad) of radiation just before it begins dividing can cause mitotic delay
know how radiation can interfere with a function of a cell
permanent or temporary interferences with cellular function can be brought on by radiation
what does oxygen enhance
the effects of ionizing radiation on tissue by increasing tissue radiosensitive
know the law of Bergonie and Tribondeau
the radiosensitivity of cells is directly proportional to their reproductive activity and inversely proportional to their degree of differentiation
know where the most pronounced radiation effects occur in a cell
in cells having the least maturity and specialization of differentiation; the greatest reproductive activity; and the longest mitotic phase
what is the sensitivity of a mature cell that is highly specialized in its function
the less sensitive it is to radiation
how does ionizing radiation affect blood cells
ionizing radiation adversely affects blood cells by depressive the number of cells in the peripheral circulation
know why epithelial tissue is highly radiosensitive
because the body constantly generates epithelial tissue, the cells that compromise this tissue are highly radiosensitive
know why muscle tissue is relatively insensitive
highly specialized and not divide
know what happens when a nerves tissues nucleus is destroyed?
cell dies and is not restored
know what happens when a nerves tissues is damaged?
may still ne able to function but in a partially impaired state
what dose causes severe damage to the CNS
excess of 50 Gy (5000 rad)
why the responses of male and female germ cells to ionizing radiation is different
because their processes of development from immature to mature status differ
why are mature spermatogonia (sperm cells) relatively insensitive to radiation
they are specialized and do not divide
know what can cause temporary and permanent sterility in sperm cells
TEMPORARY= radiation dose of 2 Gy (200 rad) for as long as 12 months
PERMANENT= a dose of 5 Gy or 6 Gy
Know the radiosensitivity of an ova cell
varies through lifetime. Immature = very radiosensitive, more mature has little radiosensitivity
know what causes temporary and permanent sterility in mature woman
TEMPORARY= 2 Gy PERMANENT= 5 Gy (500 rad)
